A vehicle driven by an engine, a motor, or the like includes a transmission for obtaining a speed, and a driving force, which both are appropriate to road conditions. The transmission is generally represented by a continuously variable transmission, an automatic transmission and a manual transmission. Generally, a manual transmission includes an input shaft for transmitting an input rotation of an engine or the like, an output shaft for transmitting an output rotation to a wheel, plural drive gears fixedly mounted on the input shaft, plural idle gears idly rotatably mounted on the output shaft and constantly meshed with the driving gears, a sleeve splined with a circumference of a hub, which is integrally rotated with the output shaft, and moved in a direction of an axis of the shaft, and a synchromesh mechanism, by which a desired shift stage is established by the sleeve synchronizingly engaged with a desired idle gear in response to a driver's operation.
According to a conventional manual transmission, a driver occasionally used to perform a shift operation as well as engaging and disengaging operations of a clutch for shifting. In a shift operation, a shift stage desired is selected and engaged with a sleeve moved in response to a shift lever operation by a driver. Recently, in order to reduce loads subjected to a driver, an automated manual transmission has been used, which basically has a manual transmission structure although performs a shift operation by means of an actuator which uses an oil pressure, or a motor, as a driving power source. One of the known automated manual transmissions is disclosed in JP2003-65434A. According to this automated manual transmission, a fully automated shift operation can be achieved by an automated manual transmission control apparatus, which controls the actuator, and a semi-automated shift operation can be also performed on the basis of a driver's intention.
In most cases, an automated manual transmission, that has a manual transmission as a basic structure, does not include a synchromesh mechanism for a reverse shift stage. If the transmission is shifted into a reverse shift stage by a mistake on the part of the driver while the vehicle is running in a forward direction, especially at a high speed, behavior of the vehicle suddenly changes and the driver is placed in a dangerous situation. In order to avoid such a situation, according to a conventional technology, when a vehicle forward driving or a brake pedal not being depressed is detected, for example, by a vehicle speed sensor provided on the output shaft, the wheel or the like, a shift operation into a reverse shift stage is effectively prevented.
However, a vehicle speed sensor has experienced difficulties in detecting the forward driving of the vehicle at a low speed because of the inadequacies of its detection capability. It on occasions may be dangerous if a shift stage is actually shifted into the reverse shift stage while the vehicle is running forward even at a low speed. Further, there may be a danger that each transmission component, such as a reverse shift stage gear, may incur serious damage. A mechanical reinforcement of the transmission for withstanding such damage and an additional loading of the synchromesh mechanism for the reverse shift stage would entail an increase in manufacturing costs of the vehicle.
A need thus exists for an automated manual transmission control apparatus which, without entailing an increase in the manufacturing costs of a vehicle, by preventing a shift operation into a reverse shift stage until the vehicle starts running at a lower speed than the above, can provide a higher degree of driving safety and reduce potential damage to a transmission. The present invention has been made in view of the above circumstances and provides such an apparatus.